Reciprocating tools that are motor driven, such as saber saws, larger reciprocating saws and the like are usually driven by electric motors that have a rotating output shaft. The rotating motion is translated into reciprocating motion for moving a saw blade or the like in a reciprocating manner. Various approaches have been developed which translate the rotational motion into reciprocating motion. A common approach is the incorporation of a wobble plate drive.
A “wobble plate” assembly is a configuration wherein a shaft has an angled portion on which an arm is mounted through a ball bearing assembly. The arm is slidingly positioned within a portion of a plunger assembly. As the angled portion of the shaft rotates, the arm translates the rotation of the shaft into a reciprocating movement of the plunger assembly. One example of a reciprocating tool which incorporates a wobble plate drive is U.S. Patent Publication No. 2011/0247847, which was published on Oct. 13, 2011, the entire contents of which are herein incorporated by reference.
As the plunger assembly moves along an axis, a significant amount of momentum is created. All of this momentum is absorbed by the tool as the plunger assembly reverses direction. Thus, a user of a reciprocating tool incorporating a wobble plate drive must contend with a powerfully vibrating device. In order to make such reciprocating tools more controllable, reciprocating tools such as the device in the '847 patent publication incorporate a counterweight which is driven by a secondary wobble plate in a direction opposite to the direction of the plunger assembly. In order to function properly, the housing enclosing the counterweight must be large enough to allow for travel of the counterweight without touching other components. Thus, while the incorporation of a secondary wobble plate and counterweight is effective, such systems can be bulky and expensive.
Moreover, the counterweight in known devices is guided by two rods. One of the rods provides primarily for guiding and aligning (eliminating the X and Y rotational degrees of freedom). The other rod is the secondary for anti-rotation (eliminating the Z rotation degree of freedom). By using the two rods, the counter balance is only allowed to slide in the X direction. The “X axis” or “X direction” as used herein refers to the direction in which a plunger reciprocates. Such a device is disclosed in the '847 patent publication.
The guide rods slide inside and are supported by guide bushings within the counterweight. There are manufacturing variations in bushing sizes and alignment, however, that cause higher friction in the sliding mechanism, generating additional non-desirable heat buildup. The heat affects efficiency and reduces the life of the mechanism.
A need exists for a reciprocating tool which reduces vibration of a wobble plate drive while reducing production of heat. A further need exists for a reciprocating tool which reduces vibration of a wobble plate drive which does not rely upon bulky assemblies. A system which reduces vibrations in a reciprocating tool while reducing costs associated with vibration reduction would be further beneficial. A system which reduces the overall size of a reciprocating tool so that it is portable and convenient to use without sacrificing the performance.